Manufacture of activated carbon



Patented Apr. 17, 1951 MANUFACTURE or ACTIVATED CARBON Joseph W.Don'egan, New Brunswick, N. J., as-

signor to Allied Chemical & Dye Corporation, New York, N. Y., acorporation of New York No Drawing. Application April 2, 1948, SerialNo. 18,712

Claims.

This invention relates to the manufacture of activatable chars andactivated carbons from bituminous. materials such as tars and pitches.

Tars and pitches, such as coal tars and watergastars and pitchesof each,provide a cheap and plentifully available source of raw material for theproduction of activated carbons suitable for use for decolorizing,deodorizing, and Water purification, and also for gas and vaporadsorption purposes. The term coal tar as used herein isintended toinclude all tars resulting from the destructive distillation of coalsand typified by such tars as coke oven tar, vertical retort tar, and gashouse tar. Conversion of carbonaceous materials into activated carbonnormally involves the carbonization or charring of the raw materialfollowed by activation of the resultant char. tar and water-gas tars andpitches of each as sources of carbon in the manufacture of acti-Previous attempts to use coal' vatedcarbon have been unsuccessfulchiefly because the pyroly'tic cokes resultingrfrom the conventionalcharring of such'materials are essentially non-porous, the pores beingso plugged with refractory hydrocarbons as to prevent access of theactivating gases to the carbon surfaces,'and no prior processes havebeen developed which adequately take into account these char-'acteristics. i

This invention provides methods the practice of which makes commerciallyfeasible the utilization of bituminous raw materials of the typesmentioned as sources of carbon for the production of activatable charsand activated carbons. Other objects and advantages of thepresent-improvements will appear from the following detaileddescription.

A preferred embodiment of the invention involves the production ofsuperior grades of activated carbons from coal tar pitches, and thedescription of the invention hereinafter given will be confined chieflyto use of these materials, although it is understood that the conditionscited are illustrative and are applicable in principle to any equivalentraw materials.

In accordance with the invention, coal tar, wa

heating in the presence of oxygen-containing gas at temperaturessufiiciently high to char the material While maintaining thetemperatures sufficiently low during such heating so that at least asubstantial proportion of the material remains in unfused condition, andheating of the material is continued until an infusible activatable charis obtained. Preferably: the material subjected to the oxidationtreatment is maintained at temperatures above 200 C. during at least thelatter stage of charring; the temperature of the material is raised frombelow 200 C. to within the range of 200-400 C. during the early portionof the charring or oxidation step and is thereafter maintained withinthe range of 200- 400 C. until an infusible activatable char isobtained. In all embodiments of the invention, at the start of thecharring operation, the material should not be initially subjected toheating at temperature higher than about 50 C. below the melting pointof the particular pitch material being utilized. More particularly, thesolvent precipitated material is subjected to an oxidation treatment atslowly increasing temperatures rising from below 200 C. and preferablyfrom below 150 C. to within the range of 200-400 C., preferably to above300 C., in the presence of a stream of oxygen-containing gas. The rateoftemperature rise during this heat treatment must be regulated inaccordance with the character of the-pitch being processed ter-gas taror pitches derived from such tars are 1 treated with a solvent,preferably an aromatic solvent, in such manner as to remove from the taror pitch a major portion of the benzol-soluble hydrocarbon constituentsthereof and obtain a solvent-precipitated pitch product in a finelypulverulent form. This material, containing a major proportion by weightof benZol-insoluble hydrocarbon constituents, is then subjected to atwhich fusion of significant proportions of the hydrocarbons constitutingthe material occurs, and the heat treatment is continued until aninfusible char is obtained. Preferably, the oxygen containing gas'abovereferred to contains from 5 to 25% byrvolume of free oxygen. Forexample, air, or a flue gas containing about 8% of oxygen, may beemployed.

Typical of the suitable raw or starting materials are coal tar pitches.Such pitches contain varying .proportions of benzol-insolublehydrocarbons and ;benzol-soluble hydrocarbons. Representative, coal tarpitches of the type referred to have softening points (cube method) of30 C. to 220 0., contain from 5% to by weight of benzol-insolublehydrocarbons, and from 40% to by Weight of hydrocarbons which aresoluble in benzol. For'purposes of this invention, the grade of pitchcommercially known as fuel pitch has been found particularly suited,pitch of this character having a softening point of C. to 200 C., andcontaining from 25% to 60% by weight of benzolinsoluble hydrocarbons.The foregoing benzolinsoluble and benzol-soluble hydrocarbons arelikewise respectively insoluble and soluble in other solvents. However,for convenience and purposes of definition, and in accordance withcurrent analytical procedure such hydrocarbons are referred to herein asbenzol-insoluble and benzol-soluble.

In carrying out a preferred embodiment of the invention, fuel pitch,after liquefaction desired, is treated with a suitable solvent, and isthereby separated into high and low melting fractions. In the solventselected, the high melting fraction (the raffinate) is substantiallyinsoluble and usually contains a major portion of the benzol-insolublehydrocarbons, while the low melting fraction (the extract) is soluble inthe solvent. These fractions then may be separated by any convenientmeans such as filtration, centrifuging or sedimentation. Satisfactorysolvents are predominantly aromatic in character and are typified by therelatively low boiling coal tar distillate boiling within the range of80 C. to 250 C., such as xylol, benzol, toluol and crude heavy solventnaphthas. The raffinate pitch is characterized by a high melting pointand a high content of benzol-insolubles whereas the extracted fractionis low melting and is substantially wholly soluble in benzol, toluol,Xylol and similar solvents.

In representative operations, fuel pitch and solvent mixtures aredigested and agitated for one or more hours at a temperature of about 90to 130 C. with about 2 to volumes of solvent per volume of pitch. Typeand quantity of solvent employed, extent of agitation, time andtemperature of treatment, may be altered within the limits indicateddepending upon the desired extent of solution of. resins and otheraromatic solubles contained in the fuel pitch. In the practice of onemethod for treating starting material with solvent, a molten coal tarpitch (e. g. 150 C. fuel pitch having 42% benzol insoluble) i cut backby slow addition of one volume of Xylol while continuouslyagitating.This homogeneous cutback pitch is cooled, preferably to about 90 C.,andthen an additional two volumes of xylol are added, agitation .being.continued. Dilution with xylol beyond the 1:1 ratio results ina breakingof the cutback, or separation into two phases, a liquid continuousphase-containing the Xylolsoluble hydrocarbons, and asolid, finelydispersed solid phase representing thosehydrocarbons which are insolublein the liquor.

In an alternative method for treating starting material, the solid pitchmaybe digested with approximately three volumes of the solvent used inthe former example, the temperature of digestion being approximately 100C. In this procedure, the soluble bitumens go into solution in thesolvent and the insoluble fraction remains in suspension as a finelydivided, easily filtered suspensoid. The precipitate formed by either ofthe foregoing digestion methods may be readily separated from thedigestion liquor as by filtration, or otherwise.

The resulting filter cake comprises the high melting,solvent-precipitated pitch together with occluded digestion liquor.Preferably, digestion is regulated to form a fiuid mass containingsolvent-precipitated hydrocarbon material which, when separated from thesolvent liquor by convenient means, contains less than 50% by weight ofbenzol-soluble hydrocarbons and a major portion by weight ofbenzol-insoluble hydrocarlower amounts of benZol-solubles.

bons. Ordinarily, the above initial digestion yields a filteredrecipitated material which may contain approximately 35-40% by weight ofbenzol-soluble hydrocarbons, although if desired the initial digestionmay be carried to a point such that the filtered hydrocarbons containeven Particularly in the former instance, further reduction of thebenzol-soluble content of the solvent-precipitated pitch and thecorresponding increase of the benzol-insoluble content may be easilyaccomplished by reslurrying or washing the initial digestion stagefilter cake with an additional quantity of any one of the suitablesolvents, usually the same solvent as used in the primary digestion. Iffound necessary, the reslurried mass may be kept at temperatures ofabout -l00 C. for one or more hours, this procedure effecting extractionof further quantities of the soluble hydrocarbons. Following one or moresuch additional digestion or washings, the finely pulverulent,precipitated hydrocarbon material containing a substantially smalleramount of associated benzol-soluble hydrocarbons is separated from thewarm wash liquor as by filtering.

Whether or not subjected to .redigestion or washing to separateadditional quantities ofhydrocarbons soluble in the solvent employed,the filter cake at hand is dried inany suitable manner, e. g. by heatingon trays at temperatures of, say, 90-100 C. in order to evaporateoffoccluded' solvent. Drying should be carriedout under such conditionsof temperatureand time as to avoid any coalescence or possible fusion ofthe powdered carbonaceous material. While drying, if the temperature iraised too rapidly as thesolvent is being eliminated, the solvent willdissolve and fiux the pitch, and a fused mass will result. Whendigestion; washing, and drying are properly carried out as described,the resulting dried intermediate product is a finely pulverulent dust,substantially all passing 325 mesh, and having the below statedcompositions and melting points.

In the practice of this invention, the raw material digestionoperations, or the combination of primary digestion and theredigestion-orwashing of the primary digestion stage filter cake, are socarried out or correlated as to produce, after drying, a finelypulverulent, relatively high melting raffinate not less than about 60%of which is insoluble in benzol. Ordinarily, the rarlinate is a materialnot less than about 70% by weight of which is benZol-insoluble and whichhas a melting point preferably not less than 200 C. In the betterembodiments of the invention, digestion, washing and drying arecontrolled and so effected that the dried raffinate-pitch analyzes notless than 75% by weight, and usually more,

of benzol-insoluble hydrocarbon and has a melting point desirably notless than 250 C. and preferably not less than 270 C. According to theinvention, it has been found that carbonaceous materials having theforegoing characteristics and derived from the starting materials hereindisclosed constitute intermediateproducts which, after selectiveoxidation in accordance with hereinafter described principles to forminfusible chars, are particularly susceptible to activation to producehigh-grade activated carbons.

Illustrative of the products formed by the foregoing solvent extractionoperations are, the following data obtained from the xylolfracitionation of a coke oven tar fuel pitch of about 160 C. meltingpoint:

' Melting point as mentioned above and as used'herein may be determinedby thefollowing procedure: About 50 mm. depth of the pulverulentmaterial is lightly tamped down into a glass tube about 4.0 mm. insidediameter and '75 mm. long which has been sealed off at one end.

"The filled tube is suspended in an electrically heated air bath and thetemperature raised gradually at a rate of about C. per minute,

up to the temperature of melting. The melting point is the minimumtemperature of the air bath at which powder in the tube shows definitesintering and coalescence of particles.

The next major step of the process is the conversion of the dried,fusible, solvent-prebipitated pitch into an infusible char. Thisconversion is effected by a selective oxidation operation by which thefusible hydrocarbon is converted to an infusible char which issusceptible to activation by known methods. Although the subsequentlydescribed selective oxidation may be applied directly to the driedrafiinate when it is in the form of a finely pulverulent dust, thedust-like particles may be consolidated in one way or another, and thengranulated to afford material of more suitable particle size for furtherprocessing. These solvent-precipitated pitches are and therefore do notrequire addition of binder for subsequent consolidating or briquetting.

The invention provides for the manufacture of activated carbon productssuitable for gas and vapor absorption and solvent recovery operations,as well as products adapted for deodoriz- ,ing and .decolorizing. If thefinal activated product isto be used for gas absorption and/or solventrecovery operations, the dry pulverulent dust is desirably briquetted incompressing machines at pressures ranging from 5,000 to 50,000 poundsper square inch, depending upon the physical structure and densitydesired in the ultimate product. The briquettes are ground, sized forexample to thru 4 on 16 mesh, and the sized material is then subjectedto the charring operation. In the manufacture of gas absorption and/orsolvent recovery types of activated carbons, briquetting is preferablyeifected at pressures of e. g. 10,000-40,000 pounds per square inch insuch a way as to produce dense briquettes having specific gravities inthe range of 1.0-1.3. For 7 production of an activated productparticularly suitable for gas masks, pressures of 15,000-25,000 poundsper square inch may be utilized in such manner as to form briquetteshaving a specific gravity of about 1.2. If the final product. is to beused primarily in pulverulent form for treating liquids, the dry dustmay be consolidated for example inflaking rolls operating at pressuresof, say, 1000 pounds per square inch, the resulting flaked materialbeing ground and sized to form granules, for exthermoplastic Thecharring stage of the invention is effected by subjecting the fusiblehydrocarbon precipitate to certain heating and oxidizing-conditions.Charring is ordinarily carried out in an externally heated retort,although heating by direct contact with suitable hot gases may beemployed. Satisfactory apparatus may comprise a rotary,

externally heated retort provided on the inside with agitating flights,equipped on one end with a gas-outlet, and on the opposite end with agas inlet connected with a suitable metering device and valves so thatcontrolled quantities of an oxidizing gas, e. g. air, may be passedthrough the retort during the heating operation.

The solvent precipitated pitch which is subjected to the charringoperation is easily fusible, and the selective oxidation and conversionof this fusible hydrocarbon material to an infusible char is anexothermic reaction. The development work on which the invention isbased shows that great care must be taken in effecting the desiredconversion to an infusible char, and a major feature of the inventionincludes the discovery of conditions which make possible such conversionof the fusible hydrocarbon precipitate to an infusible, activatablechar. In accordance with this invention, it has been found that themutually interrelated factors applicable to good embodiments of theinvention and upon which accomplishment of the desired result isdependent are the overall heating temperature range; temperaturegradient during the entire period of heating; oxygen concentration ofthe oxidizing gas used during heating; rate of supply of oxidizing gasduring the conversion operation; and heating time.

Since the dried hydrocarbon precipitate prior to charring is markedlysusceptible to fusion, great care must be exercised throughout thecharring operation as a whole, and particularly during the preliminarystages thereof. As previously indicated, the charring reactions areexothermic, and for this reason it is especially necessary to guardagainst local overheating'because, if any of the material is once fused,that portion of the batch is no longer susceptible to activation andeither a very low grade of active carbon is produced or the entire batchmust be discarded. Prevention of local overheating is largely effected bconstant agitation and the vention constitutes a selective oxidation, itis also ample through 10 on 60 mesh, and the resulting granules are thensubjected to charring.

' 1.5 cu. ft per pounds of material per minute, is satisfactory to,.supply the needed oxygen.

Further, the quantity of inert gas in the air along with the oxygencontent thereof is enough to maintain in the retort a moving gas streamof suflicient total gas volume to remove the heat of reaction from themass. While it is preferred to utilize air in the manner stated as theoxidizingcooling medium, in place of air any gas containin adequatequantities of free oxygen and inert gas maybe employed. When usingoxidizing gases other than air or its equivalent, for ex emple flueases, 's'uch latter gases may contain from to by volume free oxygen,.balance inert. Depending upon the free oxygen content of the particulargas used, 'pre'ferably th'e gas stream is flowed thru the retort at sucha rate that free oxygen is passed thru the retort i n quancity withinthe range of about 0.3-1.5 cu. ft. per 100 pounds of material perminute. Thus, in the case of use of an oxidizing gas containing "5%"free oxygen by volume, preferably the gas stream is passed thru theretort at a rate within the range of about 6-30 cu. ft. per 100 poundsof material per minute. In the circumstance of use of agas containing25% free oxygen by volume, the 'gas stream is passed preferably thru theretort at a rate within the range of about 1.2-6.0 cu. ft. per 100pounds of material per minute.

At the time of introduction into the retort, the precipitated materialitself is usually at room temperature or at temperature not higher thanthe maximum 100-11 0 C. temperature of drying. Prior to charring, thegranular material 'is in an easily fusible condition. In accordance withthe invention, during all or the charring operation temperatures aremaintained below temperatures at which fusion of any substantialproportion of the hydrocarbon material would occur. -At the beginning ofcharring, when the granular material is particularly susceptible tofusion, tem .peratures in the retort are held low. Initially, noportions of the material are heated to temperatures exceeding about C.below the mel ing point of the particular material being processed.Preferably, initially no portions of the material are heated totemperatures as high as 1 200 0. Further, in all of the betterembodiments of the invention, the material is -heated up gradually froma temperature initially not higher than about 150 C. to a temperature ofthe order of 200 C. This preliminary heating may vary to some extentwith respect to both rate of temperature increase and duration. Averagerate of temperature increase should be slow, and the temperaturegradient may be relatively linear. Duration of preliminary heating maylie within the a range of /2 to 2 hours.

In accordance with the invention, the solventprecipitated pitch isheated at gradually increasing temperatures from below 200 0.,preferably from below 150 'C., to within the range of 200- 400 C. and inthe presence of oxygen-containing gas as above indicated. It has beenfound e. g. that temperature need not be increased greatly above 200 0.,good results having been obtained with maximum temperature of about 250C. in situations in which time interval of heating is sufiicientlyextended, e. g. heating at temperature up to about 250 C. for about 8hours. Ordinarily, temperatures are radually increased from below 200 C.to within the range of 300400 C., and in the best embodiments, thegradual heating is carried substantially thru the ZOO-400 C. range, buttemperature should not be permitted to exceed 400 C. Temperaturegradient throughout the 200-400 0. range may be relatively linear, andis preferably linear withinthe ZOO-300 '0. range. Time of heating attemperatures above 200 C. is generally substantially longer than thetime interval for heating at temperatures less than 200C. Duration ofheating at temperature above 200 C. may vary from 2 to 8 hours, and ispreferably 3 to 8 hours.

Because of variable factors suchas the chemical andphysicalc'haracteristics and properties --of the pitch being =charred,efiiciency of contacting of oxidizing gas and solid material, efiiciencyof heat dissipation, size of the operation, and the equipment employed,it is notpossible to definitely state minimum and. maximum heating timeswhich are applicable in all instances. vAs will be appreciated from theabove description and the following examples, various time-temperaturecycles are permissible but all have the common requirement that theyeffect conversion of the fusible hydrocarbon to an infusible charWithout permitting fusion or leaving incompletely reacted and fusibleresidues. Thus if a sample of the charred material is heated to 1000 C.and then ground and examined, the presence of brilliant black fusedfragments indicates inadequate calcination. Practice of the inventionshows that the temperature gradient and total heating time intervalsufficient to cause conversion of fusible hydrocarbons to infusibleform, i. e. to effect complete charring, may be readily determined "oncarrying out a few preliminary runs and testing the finally activatedproducts for activity.

The charred material may be finally activated by subjecting the same tothe action of steam or fiue gases, by known procedures, whilemaintaining temperatures of the general order of 800- l200 C.

Examples of practice of the invention are as follows:

Example 1 A molten coal tar fuel pitch having a softening point (cube inair method) of about 160 C., and containing about 43% by weight ofbenzolinsoluble hydrocarbons and about-5 7% b weight of benzol-sol-ublehydrocarbons was-cut back with an equal volume of industrial .xylol. Theresultant mass was a smooth homogeneous-solution of the pitch whichremained fluidat temperatures of about -95 C. The-solution wasthen-cooled to about C. and a volume of xylol equal to the gross volumeof the homogeneous solution was added thereto while stirringcontinuously. As a result of this dilution, there was precipitated a inga melting point of about 300 C.

This dried, ,pulverulent pitch product was then briquetted at pressureof about 22,000 "lbs. per sq. in., and crushed .to thru 10 on 20 mesh,'(briquette 'density'l;20). The thus granulated high density particleswere then subjected to selective oxidation in a rotary retort equippedwith'internal flights, a gas 'outlet,'a metered and 'valve controlledgas inlet, and mounted in an electric 'mufile'furnace. The retort wasrotated at about 0.2 R. P. and the flights in the retort kept thegranular material thoroughly agitated.

Air was charged into the 'gas'inlet 'end of the retort so that,throughout the entire run, air was passed into and through the retort ata'rate or about 6 cu. ft. per lbs. of'material'per minute.Onintroduction into the retort, the material 'was at about roomtemperature. Heating by the furnace was so controlled that thetemperature of the material in the retort rose to about 200C.

in about one and one-half hours, and then was raised to 300 C. duringabout three and one-half hours, the rate of increase during this latterinterval being substantially linear. The temperature of the material wasfinally raised to approximately, but not exceeding, 400 C. over a periodof about one and one-half hours. Total heating Activated Pitch Coco-Coco- Sample Oarbons nut #1 nut #2 Sp. r. of 12/30 mesh .500 .360 .500.350 Serv1ce Time-C014 18% 19 14 14 Capacity-C C14:

guns/gm. Carbon 0.82 1. 28 0.68 1. 08 gms./cc. Carbon 0.41 0.45 0.340.38

The carbon tetrachloride test is that described by Fieldner et al.,Industrial and Engineering Chemistry, II, 519 (1919) using air at 25 C.containing 40,000 P. P. M. of carbon tetrachloride.

Example 2 A coal tar fuel pitch, obtained by distillation of coke oventar, having a softening point of about 150 0., and containing about 42%by weight of benzol-insoluble hydrocarbons and about 58% by weight ofbenzol-soluble hydrocarbons was pulverized and digested with about 2 /2volumes of xylol for, 2 hours at a temperature of about 90-130 C. Theslurry was filtered, and the insoluble material was obtained as a filtercake containing about 30% by weight of benzolsoluble hydrocarbons. Thefilter cake was reslurried and washed with another 2% volumes of xylol,and there was obtained, after tray drying at about 110 C., a pulverulentpitch containing about 77% by weight of benzol-insoluble hydrocarbonsand about 23% by weight of benzolsolubles, and having a melting point ofabout 295 C. q The dried powder was then briquetted at pressure of about20,000 lbs. per sq. in., and crushed to through 6 on 20 mesh. The thusgranulated material was then subjected to selective oxidation in arotary retort of-the type of Example 1.

The retort was rotated at about 0.2 R. P. M., and the flights in theretort kept the granular material thoroughly agitated. Air was chargedinto the gas inlet end of the retort so that, throughout the entire run,air was passed into and through the retort at a rate of about 6 cu. ft.per 100 lbs. of material perminute. On introduction into the retort, thematerial was at about room tempera ture. The heating cycle wassubstantially the same as that of Example 1. The resulting carbonaceouschar was then activated with steam in accordance with known procedure attemperature of about 975 C. to a weight loss of about 60%. A 0.25 gramsample of the product, crushed to pass a 200 mesh screen, adsorbed 92%of the iodine from a standard iodine solution. The activated material,when crushed to thru 12 on 16 mesh, had a bulk density of. 0.500 and,when exposed to an atmosphere containing 40,000 P. P. M. of carbontetrachloride at 25 C., ad-

sorbed of its own weight of carbon tetra- Example 3 A flaked fuel pitchobtained by vacuum distillation of water gas tar and which wascharacterized by a softening point of'about 150 C.'and abenzol-insoluble content of 31%, was extracted by digestin with 3volumes of a crude solvent naphtha boiling within the range of 125 to250 C. Digestion was effected by adding the cold pitch to the coldsolvent and agitating continuously while raising the temperature to C.over a one-hour period. Theresultant slurry was filtered, and the cakewas washed with an additional 3 volumes of the solvent so that there wasobtained, after drying at about C., a carbonaceous product comprisingapproximately 30% benzol-insoluble hydrocarbons and 20% benzol-solublecomponents. The melting point of this product was about 310 C.

The pulverulent pitch product was lightly compacted by passing thru adifferential speed roll mill and the resultant flake was granulated toprovide low density grain of 10 to 20 mesh size. Calcination forconversion into a, suitable infusible char was carried out by heating inthe appa ratus of the preceding examples. On introduction into theretort, the material was at about room temperature. However, in thisoperation, instead of air, a, flue gas containing 10% oxygen was passedthrough the retort at the rate of about 10 cu. ft. per 100 lbs. ofmaterial per minute. The heating cycle followed was substantially thesame as that of Example 1, and a well? calcined char was produced.

After calcination, the char was activated by heating to 1100 C. Whilepassing carbon dioxide thru the retort. The activated product,representing 30% of the char, was of such activity that 0.5 gram removed91% of the color from a standard brown sugar solution. A high grade ofcommercial decolorizing carbon removed 88% of the color in a comparabletest.

Example 4 A coke oven tar fuel pitch was produced by air blowing aresiduum of 66 C. softening point until the product had a softeningpoint of 219 C. and a benzol-insoluble content of 50%. This pitch wasfractionated by extraction ofthe pulverized pitch with 5;volumes ofcrude solvent naphtha boiling within the range of to 250 C. The;

charged, at about room temperature, into the V retort of Example 1.Conversion to a satisfactory char was efiected on the following heatingcycle: One and one-half" hours to 200 C., two hours from 200 to 300. 0.,and one hour from. 30.0 to 400 C. Throughout the calcination, air waspassed through the retort at the rate of about 6 cu. ft. per 100 lbs. ofmaterial per minute.

The calcination product was adequately charred and completely infusible.After activation with steam at 1000 C. to 60% weight loss, the grain hada carbon tetrachloride service time of 20 minutes, a capacity of .820gram C614 per gram of carbon, and a heat of wetting with xylol of 23calories per gram.

Example Precipitated pitch hydrocarbon, obtained from the same coal tarfuel pitch, by substantially the same extraction procedure, and havingsubstantially the same properties, all as in Example 2, was briquettedat 20,000 lbs. per sq. in. and then granulated to -20 mesh size. Theresultant material was charged into the retort of Example 1. The retortwas rotated at about 0.'2 R. P. M., and the flights in the retort keptthe granular material thoroughly agitated. Air was charged into the gasinlet end of the retort so that, throughout the entire run, air waspassed into and through the retort at a rate of about 3 cu. ft. per 100-lbs. of material per minute. On introduction into the retort, thematerial-was at about room temperature. The temperature was raised to200 C. in one hour, and then gradually raised to. about 250 C. over aperiod of about 8 hours. The material was completely converted to aninfusible char, and'on activation with steam at 1000 0., yielded aproduct giving 20 minutes service time in the C014 test;

The benzol-insoluble contents and cube melting and softening points ofthe materials referred to herein are determined by standard testsprescribed in Methods of Testing Coal-Tar Products (revised July 1942),published by The Barrett Division, Allied Chemical & Dye Corporation, 40Rector Street, New'York, copyright Allie Chemical: & Dye Corp. 1931 and1942.

I claim:

1. The process for making an activatable char from a solid carbonaceousmaterial containing not less than 60% by Weight of benzol-insolubleconstituents derived from starting material of the group consisting ofcoal tar andwater-gas tar and pitches of each, which comprises'heatingsaid derived carbonaceous material at increasing-temperatures from below200 C. to within the range of 200-400 C. in the presence of freeoxygencontaining gas, the free oxygen concentration of said gas beingsufliciently high to selectively oxidize and convert said carbonaceousmaterial to an infusible char, maintaining the temperatures of saidcarbonaceous material'during heating below temperatures at which fusionof a substantial proportion of the carbonaceous material would occur,and continuing heating until an infusible activatable char is obtained.

2. The process for making an activatable char which comprises extractinghydrocarbon material of the group consisting of coal tars, watergas tarsand their pitches with a predominantly aromatic solvent to producehydrocarbon material containing not less than 70% byweight ofbenzol-insoluble constituents, heating said lastnamed hydrocarbonmaterial at gradually increasing temperatures from below 200 C. towithin the range of 200-400 C. in the presence of free oxygen-containinggas, .the ee oxygen to selectively oxidize and convert said last-namedhydrocarbon material to an infusible char, maintaining the temperaturesof said material throughout said heating period below temperatures atwhich fusion or" a substantial proportion of the hydrocarbonsconstituting the material would occur, and continuing said heattreatment until an infusible activatable char is obtained.

3. The process for making an activatable char from a solid carbonaceousmaterial containing not less than 70% by weight of benzol-insolubleconstituents and having a melting point not less than 200 C. and derivedfrom starting material of. the group consisting of coal tars, water-gastars and their pitches, said process comprising heating said derivedcarbonaceous material at gradually increasing temperatures from below200 C. to Within the range of 200400 C. in the presence of a' gascontaining 5-25% by volume free oxygen, maintaining the temperature ofthe thus heated material at all times throughout said heating periodbelow the temperature at which fusion of a substantial proportion of thesolids present in said material at that time would occur, and continuingsaid heating above 200 C. until an infusible activatable char isobtained.

4. The process for making an activatable char which comprises extractinghydrocarbon material of the group consisting of coal tars, watergas tarsand their pitches with a predominantly aromatic solvent to producehydrocarbon material in a finely pulverulent form and containing a majorportion by weight of benzol-insoluble hydrocarbons and having a meltingpoint not less than 200 C., heating said last-named hydrocarbon materialat gradually increasing temperatures from below 200 C. to within therange of 200 400' C. in the presence of a gas containing at least 5% byvolume free oxygen, maintaining the temperatures of said materialthroughout said heating period below temperatures at which fusion of asubstantial proportion of the hydrocarbons constituting the materialwould occur, and continuing said heat treatment until an infusibleactivatable char is obtained.

5. The process for making an activatable char which comprises forming asolid material containing not less than 70% by weight of benzolinsolublehydrocarbons, having a melting point not less than 200 C. and derivedfrom starting material of the group consisting of coal tar and water gastar'and pitches of each, heating said solid material at graduallyincreasing temperatures from below 200 C. to within the range of 200-400C., carrying out said gradual heating operation, substantially thru said200-400 C. range but to temperature not exceeding 400 C.. in thepresence of a gas containing 5-25% by volume free oxygen, maintainingthe temperatures of said material throughout said heating period belowtemperatures at which fusion of a substantial proportion of thehydrocarbons constituting the material would occur, and continuing saidheat treatment until aninfusible activatable char is obtained.

6. The process for making an activatable char which comprises forming asolid material containing not less than 70% by weight of benzolinsolublehydrocarbons and derived from starting material of the group consistingof coal tar and water-gas tar and pitches of each, heating said solidmaterial at gradually increasing temperatures from below 200 C, toWithin the range of 200-400 C., carrying out said gradual heat- 7 a ratesuch as to pass thru said material free oxygen within the range 0.3-1.5cu. ft. per 100 lbs. of material per min., and continuing said heatingoperation for a time interval sufiicient to effect conversion of saidmaterial to an infusible activatable char.

'7. The process for making an activatable char which comprises forming asolid material containing not less than 70% by weight of benzolinsolublehydrocarbons, having a melting point not less than 200 C. and derivedfrom starting material of the group consisting of coal tar and water-gastar and pitches of each, heating said solid material in granular form atgradually increasing temperatures from below 200 C. to within the rangeof 200-400 C., carrying out said gradual heating operation (1)substantially thru said 200-400 C. range but to temperature notexceeding 400 C., (2) while agitating, and (3) while passing thru saidagitated material a stream of a gas containing at least 5% by volumefree oxygen at a rate such as to pass thru said material free oxygenwithin the range 0.3-1.5 cu. ft. per 100 lbs of material per min., andcontinuing said heating operation for a time interval sufiicient toeffect conversion of said material to an infusible activatable char.

8. The process for making an activatable char which comprises forming asolid material containing not less than 70% by weight of benzolinsolublehydrocarbons, having a melting point not less than 200 C., and .derivedfrom starting material of the group consisting of coal tar and water-gastar and pitches of each; heating said solid material in granular form atgradually increasing temperatures from below 200 C. to Within the rangeof 200-400 C., carrying out said gradual heating operation 1)substantially through said 200-400C. range but to temperature notexceeding 400 C., (2) while agitating,

and (3) while passing through said agitated material a gas stream,containing 5-25% by volume free oxygen, at a rate such as to passthrough said material free oxygen within the range 0.3-1.5 cu. ft. per100 lbs. of material per min., and continuing said heating operationabove 200 C. for a time interval within the range of 2-8 hours andsuflicient to effect conversion of said material to an infusibleactivatable char.

9. The process for making activated carbon which comprises formin asolid material containing not less than 75% by weight ofbenzol-insoluble hydrocarbons, having a melting point not less than 250C., and derived by solvent precipitation from starting material of thegroup consisting of coal tar and Water-gas tar and pitches of each,heating said solid material in granular form at gradually increasingtemperatures from below 150 C. to within the range of 200-400 C.,carrying out said gradual heating operation (1) substantially throughsaid 200-400 C. range but to temperature not exceeding 400 C., (2) whileagitating, and (3) while passing thru said agitated material a stream ofair at a rate within the range 1.5-7.5 cu. ft. per 100 lbs. of materialper min., continuing said heating operation above 200 C. for a timeinterval within the range of 2-8 hours and sufficient to efiectconversion of said material toan infusible activatable char, and thensubjecting the thus heat treated material to the action of carbonactivating medium at temperature above 800 C.

10. The process for making a hard dense acpulverulent materialcontaining not less than by weight ofbenzol-insoluble hydrocarbons andhaving a melting point not less than 250 C., compressing the materialunder pressure suificient to form dense briquettes having specificgravity in the range of 1.0-1.3, heating said briquetted material ingranular form at gradually increasing temperatures from below 150 C.-towithin the range of 200-400 C., carrying out said gradual heatingoperation 1) substantially through said 200-400 C. range but totemperature not exceeding 400 C., (2) while agitating, and (3) whilepassing thru said agitated material a stream of air at a rate within therange 1.5-7.5 cuxft. per. lbs. of material per min.; continuing saidheating operation above 200 C. for a time interval within the range of2-8 hours and sufficient to effect conversion of said material to aninfusible activatable char, and then subjecting the thus heat treatedmaterial to the action of carbon activating medium at temperature above800 C.

JOSEPH W. DONEGAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,553,641 Sperr Sept. 15, 19251,731373 Naugle Oct. 15, 1929 OTHER REFERENCES Deitz: Bibliography ofSolid Adsorbents, page 776, 2nd paragraph (1944) British' ChemicalAbstracts-B, pages 1098-9 1930).

1. THE PROCESS FOR MAKING AN ACTIVATABLE CHAR FROM A SOLID CARBONACEOUSMATERIAL CONTAINING NOT LESS THAN 60% BY WEIGHT OF BENZOL-INSOLUBLECONSTITUENTS DERIVED FROM STARTING MATERIAL OF THE GROUP CONSISTING OFCOAL TAR AND WATER-GAS TAR AND PITCHES OF EACH, WHICH COMPRISES HEATINGSAID DERIVED CARBONACEOUS MATERIAL AT INCREASING TEMPERATURES FROM BELOW200* C. TO WITHIN THE RANGE OF 200*-400* C. IN THE PRESENCE OF FREEOXYGENCONTAINING GAS, THE FREE OXYGEN CONCENTRATION OF SAID GAS BEINGSUFFICIENTLY HIGH TO SELECTIVELY OXILDIZE AND CONVERT SAID CARBONACEOUSMATERIAL TO AN INFUSIBLE CHAR, MAINTAINING THE TEMPERATURE OF SAIDCARBONACEOUS MATERIAL DURING HEATING BELOW TEMPERATURE AT WHICH FUSIONOF A SUBSTANTIAL PROPORTION OF THE CARBONACEOUS MATERIAL WOULD OCCUR,AND CONTINUING HEATING UNTIL AN INFUSIBLE ACTIVATABLE CHAR IS OBTAINED.